Revert "PCI: Introduce domain_nr in pci_host_bridge"

This reverts commit d9b8b8f3 which is
commit 15d82ca2 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Ie1b8840de6c8ef51328f4515bd337d56ee055e61
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>